Complex query using Criteria API in Hibernate 4

Question

I am using hibernate 4 with criteria API and I am facing a complex query.

My relational model is the following:

What I am trying to do is to get for a given Person all the shipped Articles that belongs to the "n" last ShoppingEvent before a specified date.

How can I achieve that using criteria API?

nb I already tried something like:

ProjectionList properties = Projections.projectionList();
properties.add(Projections.property("article.articleId"), "articleId");
properties.add(Projections.property("article.price"), "price");
properties.add(Projections.property("article.type"), "type");

return session.createCriteria(Person.class)//
         .add(Restrictions.idEq(person.getPersonId()))//
         .createAlias("articles", "article")//
         .createAlias("article.shoppingEvent", "se")//
         .add(Restrictions.le("se.date", currentDate))//
         .addOrder(Order.desc("se.date"))//
         .setProjection(properties)//
         .setResultTransformer(Transformers.aliasToBean(Articles.class))//
         .list();

Which returns the articles I want but I don't succeed to use the setMaxResults to limit the max number of ShoppingEvents .

Answer 1

It would be easier if you build your query based on the Article, it would be like this:

ProjectionList properties = Projections.projectionList();
properties.add(Projections.property("id"), "articleId");
properties.add(Projections.property("price"), "price");
properties.add(Projections.property("type"), "type");

return session.createCriteria(Article.class) 
 .createAlias("person", "person") 
 .createAlias("shoppingEvent", "shoppingEvent") 
         .add(Restrictions.idEq(person.getPersonId()))  
         .add(Restrictions.le("shoppingEvent.date", currentDate)) 
         .addOrder(Order.desc("shoppingEvent.date")) 
         .setProjection(properties) 
         .setResultTransformer(Transformers.aliasToBean(Articles.class)) 
         .setMaxResults(1)
         .uniqueResult();

I mean I get the "n" last Articles but not all the Articles of the last "n" ShoppingEvent

To do this just specify "n" in the .setMaxResults( n )

Answer 2

您可能想尝试一个DetachedCriteria，让它返回上一个ShoppingEvent的“ n”个ID，然后在您的条件中添加一个限制，使您的article.shoppingEvent必须与detachedCriteria中的ID列表匹配。